1. Field of the Invention
The invention pertains to sheet fed platen presses incorporating a stripping station for stripping waste from a die cut sheet wherein sheets are individually transported by gripper bars supported by endless chains or their equivalent to the stripping station and the stripping is effected by relative movement between a templet having perforations corresponding to the waste to be stripped from the die cut sheet and a support having stripping fingers connected thereto which engage the waste and force it through the perforations in the templet.
2. Prior Art
In stripping devices which have heretofore been used in sheet fed presses and which includes a fixed upper part and a movable lower perforated plate or part, the die cut sheet as well as the means of conveyance means for conveying the sheet (usually chains) carry out a vertical upward and downward movement during the stripping operation. The fixed upper part of such a stripping device includes stripping tools arranged opposite the apertures of the perforated plate. The apertures of the perforated plate have outlines which correspond generally to the outlines of the waste to be stripped from the sheet. Hence, when the vertical motion of the movable lower part takes place the lower part raises the sheet, and the waste will enter into contact with the stripping tools and drop from the sheet while the sheet continues its vertical motion with the lower plate or part. Then, the movable lower part will take up its starting or lower position so that the sheet, now stripped of waste, can be withdrawn from this stripping station by means of the conveying chains. During the whole stripping operation, the sheet is held in position by a gripper bar connected to the means of conveyance which gripper bar and means of conveyance have also undergone an upward motion. However, the lifting of the means of conveyance, once they have come to a resting position during a dwell period of advancement occurs when the frame of the movable lower part enters into contact with the means of conveyance resulting in a rather strong hit or blow to the means of conveyance which blow or hit raises the operating sound level of the machine and interferes with the stripping operation by causing vibrations. This striking of the chains when they are in their rest positions also occurs upon return motion of the movable lower part of the stripping station to its starting position due to the fact that the conveyance chains drop onto their respective chain guides with a rather sharp blow. Moreover, these repeated blows are harmful for the mechanical service life of the means of conveyance and their associated parts particularly in view of the fact that on present day platen presses the stripping operation may be repeated as frequently as 6500 times per hour.